Dual mode seat belt retractor assembly

ABSTRACT

This invention relates to a seat belt retractor for a motor vehicle which can be operated in an emergency locking mode wherein belt retraction is prevented only upon vehicle deceleration, or in an automatic locking mode where the retractor operates as a one-way clutch to inhibit belt withdrawal. A mode switching mechanism is provided which causes the operating mode of the retractor to change when the seat belt webbing is either fully extended or fully retracted. The mode switching mechanism employs a rotating actuator ring gear having one or more tabs which engage an actuator lever which is caused to move between two positions. In one position of the actuator lever, the locking bar of the retractor is urged into engagement with the toothed sprockets of the retractor causing the retractor to operate in the automatic locking mode. In the other position of the actuator lever, biasing of the locking bar is relieved so that the retractor operates in the emergency locking mode. The design according to this invention provides wide flexibility in terms of packaging of the retractor and is easily modified to accomodate various lengths of seat belt webbing.

This is a continuation of patent application Ser. No. 788,021, filed10/16/85, now U.S. Pat. No. 4,726,539.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a motor vehicle seat belt retractor andparticularly to a retractor which can be operated either in emergencylocking or automatic locking modes.

Most motor vehicles are equipped with seat belt systems which, whenused, restrain the occupants when the vehicle is subjected to high ratesof deceleration which may occur during a collision. Many seat beltretractor designs are of the so-called emergency locking type. Theseretractors employ an inertia sensitive actuator which prevents seat beltwebbing from being withdrawn from the retractor when the vehicle issubjected to deceleration forces above a predetermined level, therebyrestraining the vehicle occupant. During normal conditions, however, theseat belt webbing may be freely withdrawn from the retractor, providingthe occupants with freedom of movement.

Another type of seat belt retractor is often referred to as an automaticlocking retractor. These retractors act as a one-way clutch in that oncewithdrawal of the belt webbing is stopped, further withdrawal of thewebbing is prevented. When, however, the seat belt is unfastened and thewebbing is fully retracted within the retractor, the webbing can againbe withdrawn to the desired extent. These types of retractors firmlyrestrain the occupant since webbing cannot be withdrawn and thereforerestrict freedom of movement of the occupant.

The emergency locking retractor design has many advantages in terms ofoccupant comfort and convenience since they permit free movement of theoccupants until the vehicle is subjected to deceleration forces above apredetermined level. Emergency locking retractors have been foundundesirable, however, when they are used to fasten a child restraintsystem within the vehicle. For this application, it is preferred thatthe seat belt system firmly and securely anchor the child restraintsystem to the vehicle. Since automatic locking retractors do not permitfree withdrawal of webbing, they are preferably for restraining childrestraint systems. In addition, certain segments of the publicexperience a lack of confidence as to the operation integrity of seatbelt retraction mechanisms of the emergency locking type.

Due to the conflicting needs of providing adult occupant comfort andconvenience, and securely fastening child restraint systems withinvehicles, it is desirable to provide a dual mode seat belt retractorwhich may be converted between emergency locking and automatic lockingoperating modes in accordance with the needs of the user. It istherefore a principal object of this invention to provide such a dualmode seat belt retractor. It is a further object of this invention toprovide a dual mode retractor which is easily switched betweenoperational modes. It is yet another object of this invention to providea dual mode seat belt retractor which is simple in design andinexpensive to produce.

In U.S. Pat. No. 4,555,075, entitled "Dual Mode Seat Belt RetractorAssembly", and assigned to the assignee of this application, a retractorfulfilling the above-described objects is disclosed. That retractordesign, however, has somewhat limited adaptability to various motorvehicle designs and retractor placements since the inertia sensitivependulum is mounted near the center of the retractor, rather than ateither end thereof. The placement of the pendulum is restricted for thatdesign since the emergency and automatic mode switching mechanism isattached to one end of the retractor, and the retractor rewind spring isconnected to the other end of the retractor. Furthermore, the retractoraccording to the above-cited U.S. Patent is not easily adapted for seatbelt webbings having various lengths since the number of rotations ofthe retractor spool between the points at which the operating mode isswitched is relatively difficult to adjust. It is therefore anotherobject of this invention to provide a dual mode retractor which providesgreater flexibility in the mounting location of the inertia sensitivependulum actuator, and further, one that enables the retractor toaccommodate various lengths of belt webbing without major modifications.

The above objects of this invention are provided by a retractor designwhich includes a mechanism positioned at one end of the retractor forswitching the retractor between operational modes. The mode switchingmechanism includes a drive gear which causes a ring gear to rotate withrotation of the retractor spool. Extending tabs are provided on the ringgear which interact with a mode switching lever which, in one position,biases a locking bar into engagement with toothed sprockets of the spoolsuch that the retractor operates as an automatic locking retractor. Whenthe mode switching lever moves to another position, it disengages thelocking bar so that the retractor functions as an emergency lockingretractor. The retractor rewind spring assembly is preferably stackeddirectly on the housing which encloses the mode switching mechanism.Accordingly, a retractor is provided having one opened end which can beused to mount the inertia sensitive pendulum and associated components.The retractor according to this invention is easily modified toaccommodate various webbing lengths merely by changing the point atwhich the ring gear tabs protrude from the ring gear.

Additional benefits and advantages of the present invention will becomeapparent to those skilled in the art to which this invention relatesfrom the subsequent description of the preferred embodiments and theappended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of the dual mode retractor accordingto this invention;

FIG. 2 is an exploded pictorial view of a portion of the retractorframe, the mode switching mechanism, and the rewind spring assembly ofthe retractor according to this invention;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1 showingthe mode switching mechanism at a position causing the retractor tooperate in the emergency locking mode; and

FIG. 4 is a cross-sectional view also taken along line 3--3 showing theretractor according to this invention wherein the mode switchingmechanism is in a position causing the retractor to operate in theautomatic locking mode.

DETAILED DESCRIPTION OF THE INVENTION

A dual mode seat belt retractor assembly according to this invention isshown in each of the Figures and is generally designated by referencecharacter 10. Retractor assembly 10 includes rotatable spool 14 mountedto retractor frame 12. Spool 14 includes belt support shaft 16 having apair of radially extending and separated toothed sprockets 18 and 20.One end of seat belt webbing 24 is connected to belt support shaft 16and becomes rolled thereon as spool 14 is rotated. Retractor frame 12includes one or more mounting holes 26 for fasteners which permit secureattachment of retractor 10 to the associated vehicle or structure.Rotation of toothed sprockets 18 and 20 in the direction of beltextension (counterclockwise in FIGS. 3 and 4) is selectively arrestedthrough movement of locking bar 28 which is movable between positions ofengagement and disengagement with the toothed sprockets.

When retractor 10 is operating in the emergency locking operating mode,locking bar 28 is caused to move between engaged and disengagedpositions by inertia sensitive actuator 30 which is positioned at oneend of retractor frame 12. Retractor 10 may be provided with any type ofinertia sensitive actuator device. Actuator 30 is of prior art designand is briefly described herein for illustration only. Referring to FIG.1, inertia sensitive actuator 30 includes pendulum 32 which is suspendedfrom actuator frame 34 and moves in response to vehicle acceleration anddeceleration (or due to tipping of the retractor from its normalposition). The upper portion of pendulum 32 defines a button shaped top36 which urges locking lever 38 upwardly in response to vehicledeceleration above a predetermined level. Locking lever 38 has a pair ofarms (not shown), one for engaging spur gear 40 and another which actson locking bar 28. Once pendulum 32 becomes tipped due to deceleration,locking lever 38 is raised such that one of its arms engages spur gear40 which, due to rotation of spool 14 caused by belt extension, causesthe other arm of locking lever 38 to urge locking bar 28 into theengaged position. A more complete description of the configuration andoperation of elements making up an illustrative inertia sensitiveactuator 30 is provided in issued patents, U.S. Pat. No. 4,069,987,issued Jan. 24, 1978, entitled "Inertia Locking Seat Belt Retractor",and U.S. Pat. No. 4,518,132, issued May 21, 1985, entitled "CombinationSeat Belt Retractor Mechanism". The above-mentioned patents are herebyincorporated by reference.

In accordance with this invention, mode switching mechanism 44 ismounted to retractor frame 12 at the end of frame 12 opposite inertiasensitive actuator 30. Mode switching mechanism 44 is enclosed by ahousing defined by gear retainer 46 and retainer cover 48. Gear retainer46 is attached to retractor frame 12 and has a central hole 50 throughwhich belt support shaft 16 extends. Gear retainer 46 further definesseveral pockets including gear train pocket 52 and switching leverpocket 54. Switching lever pocket 54 defines a pair of posts 56 and 58,and a pair of slots 60 and 62. Slot 62 enables end tab 89 of locking bar28 to be positioned in switching lever pocket 54.

Drive gear 64 is installed onto belt support shaft 16 for rotationtherewith. As shown in FIG. 2, drive gear 64 includes central web 66which is received by slot 68 of belt support shaft 16 so that rotationof the belt support shaft drives gear 64. Reduction gear 70 definessmall toothed portion 72 and large toothed portion 74 which meshes withdrive gear 64. Reduction gear 70 is journalled for rotation in bore 76.Ring gear 78 is a relatively large gear having internal teeth and isdriven by toothed portion 72 of reduction gear 70. Ring gear 78 ispositioned by circular groove 80 within gear retainer 46. Theabove-described arrangement causes ring gear 78 to rotate with rotationof belt support shaft 16 at a reduced rate and in the oppositerotational direction. Preferably, the number of teeth of gears 64, 70and 78 are selected such that ring gear 78 undergoes approximately onerevolution between full extension and complete retraction of beltwebbing 24. Ring gear 78 defines a pair of extending tabs 82 and 84. Asbest shown in FIG. 2, tabs 82 and 84 may be displaced such that they liein parallel but spaced apart planes.

Mode switching lever 86 defines a central bore 87 which enables it to bemounted for pivoting movement onto post 58. Mode switching lever 86includes four extending arms: locking bar arm 88, tab engaging arms 90and 92, and spring arms 94. Pin 96 on spring arm 94 travels in slot 60to limit the range of angular motion of mode switching lever 86. Asswitching lever 86 moves between its extreme positions locking bar arm88 moves between an emergency locking position and an automatic lockingposition, corresponding to the operating modes of retractor 10. Modeswitching lever 86 is maintained in either the automatic or emergencylocking position by switching lever spring 98 having a horseshoe shapewith ends engaging pin 96 and post 56. The location of the pivot post 58for switching lever 86 is such that the extension force exerted byspring 98 is directed on one side of a line between posts 56 and pivot58 in one position, and the other side thereof in the other modeposition. In the automatic locking position, locking bar arm 88 urgesend tab 89 of locking bar 28 into engagement with toothed sprockets 18and 20. Once locking bar 28 engages toothed sprockets 18 and 20,withdrawal of webbing 24 is inhibited. In this operating mode, however,webbing 24 may be retracted since locking bar 28 can "ride up" the teethof sprockets 18 and 20 when spool 14 is rotated in that direction. Suchratcheting is permitted since mode switching lever 86 can be rotatedslightly with movement of locking bar 28 without switching to theemergency locking position. In the emergency locking position, lockinglever arm 88 is moved away from locking bar 28 so that the locking barwill engage toothed sprockets 18 and 20 only when urged by inertiasensitive actuator 30.

Retainer cover 48 is adapted to enclose gear retainer 46 and to trap thecomponents therein. Retainer cover 48 includes a plurality of extendingbushing shaped posts 102 that are closely received by holes 100 in gearretainer 46. Retainer cover 48 further defines a hole 104 which receivesmode switching lever 86. Extending web portion 106 supports belt supportshaft 16 and reduction gear 70. Retainer cover 48 further has acentrally disposed hole 108 allowing belt support shaft 16 to extendtherethrough.

Rewind spring assembly 110 is comprised of coil rewind spring 112 andcover 114. Cover 114 defines a pocket for attachment of one end ofrewind coil spring 112 and the other end of the spring engages slot 68of belt support shaft 16 to rotatably bias the shaft. Cover 114 becomesattached to mode switching mechanism 44 and retractor frame 12 bythreaded fasteners 116. Rewind spring assembly 110 rotationally biasesspool 14 to rewind webbing 24 in a conventional fashion. Due to theplacement of rewind spring assembly 110 directly stacked on modeswitching mechanism 44, greater flexibility in the positioning ofinertia sensitive actuator 30 is provided. As described previously,inertia sensitive actuator 30 may be provided at the opposite end ofretractor frame 12 from mode switching mechanism 44 or may be locatednear the midline of spool 14, or at any other location.

The operation or mode switching mechanism 44 is best explained withparticular reference to FIGS. 3 and 4. FIG. 3 illustrates retractor 10when webbing 24 is being retracted, causing spool 14 to rotate in aclockwise direction. Such movement of spool 14 causes rotation of ringgear 78 in a counterclockwise direction and at a reduced rate. Uponsufficient rotation, tab 84 engages tab engaging arm 90 of modeswitching lever 86, causing the lever to rotate clockwise. Uponsufficient movement, lever 86 moves to its extreme clockwise position,as shown in FIG. 3. Due to the biasing exerted by switching lever spring98. lever 86 remains in the position shown in FIG. 3 wherein lockinglever arm 88 is moved out of engagement with locking bar 28, andconsequently, retractor 10 operates in the emergency locking mode. Inthis operating mode, locking bar 28 moves into engagement with sprockets18 and 20 only in response to inertia sensitive actuator 30.

FIG. 4 illustrates the operation of retractor 10 during belt extension.Withdrawal of webbing 24 causes spool 14 to rotate in a counterclockwisedirection, causing ring gear 78 to rotate in a clockwise direction. Uponsufficient rotation of ring gear 78, tab 82 contacts tab engaging arm 92of switching lever 86 to rotate the lever in a counterclockwisedirection to the position shown in FIG. 4. In that position, lockinglever arm 88 acts upon locking bar 28 to cause it to be moved intoengagement with the teeth of sprockets 18 and 20, which are shown inphantom lines in that figure. If tension on webbing is relaxed, rewindspring assembly 110 causes belt retraction, which is permitted sincelocking bar 28 can ratchet between teeth on the sprockets, causingslight rotation of switching lever 86 (but not enough to cause the leverto move to the emergency locking position).

The position at which the above described mode switching action occursis preferably such that, at near full belt extension, the retractorswitches to automatic locking mode as shown in FIG. 4. Upon near fullretraction of the belt, retractor 10 returns to emergency lockingoperation. Therefore, during normal use of retractor 10, when the beltis not fully extended, the user is provided with a retractor whichoperates in the emergency locking mode. If, however, the user desiresthe retractor to operate in an automatic locking mode, webbing 24 isfully extended thereby changing the operating mode of the retractor.

Mode switching mechanism 44 easily accommodates various lengths ofwebbing 24 merely by changing the position of tabs 82 and 84. The tabsmay be formed integrally with ring gear 78 or as separate attachedcomponents. Further, greater flexibility is provided by enabling ringgear 78 to undergo slightly more than one revolution between its extremepositions. This is achieved by providing tabs 82 and 84 which are offsetand similarly offsetting tab engaging arms 90 and 92 of switching lever86 so that tab 82 only engages arm 92, and tab 84 only engages arm 90.

While the above description constitutes the preferred embodiments of thepresent invention, it will be appreciated that the invention issusceptible to modification, variation and change without departmentfrom the proper scope and fair meaning of the accompanying claims.

What is claimed is:
 1. In a seat belt retractor of the type having aretractor frame, a spool carried by said frame defined by a belt supportshaft and having at least one toothed sprocket, seat belt webbingconnected to said spool, a locking bar carried by said frame and movablebetween an engaged position with said toothed sprocket, therebyinhibiting withdrawal of said webbing, to a disengaged position fromsaid toothed sprocket, thereby permitting withdrawal of said webbing,said retractor further having an inertia sensitive actuator which actsupon said locking bar in response to deceleration forces above apredetermined level to urge said locking bar into said engaged position,the improvement for enabling said seat belt retractor to be operatedeither as an emergency locking retractor which prevents said seat beltwebbing from being withdrawn when said retractor is subjected todeceleration above said predetermined level, or as an automatic lockingretractor which permits retraction of said webbing but inhibitswithdrawal of said webbing, comprising:gear retainer means, gear meansdisposed in said gear retainer, said gear means driven by rotation ofsaid spool and including a ring gear, said toothed sprocket being fixedto said shaft, tab means on said ring gear, a mode switching leverhaving a spring arm and being rotatable about a pivot means from anengaged position directly contacting said locking bar and resilientlyurging said locking bar into engagement with said toothed sprocket to adisengaged position from said locking bar, spring means acting on afixed point on said mode switching lever spring arm to exert anextension force between a mounting point and said mode switching leverspring arm wherein when said mode switching lever is in said engagedposition said extension force is directed along one side of a linebetween said mounting point and said pivot means thereby biasing saidmode switching lever in said engaged position, and wherein when saidmode switching lever is in said disengaged position said extension forceis directed along an opposite side of said line thereby biasing saidmode switching lever in said disengaged position whereby rotation ofsaid ring gear causes said tab means to engage said mode switching leverto move said mode switching lever between said engaged and disengagedpositions whereby said retractor functions as an automatic lockingretractor when said mode switching lever is in said engaged position oran emergency locking retractor when said mode switching lever is in saiddisengaged position.
 2. The seat belt retractor according to claim 1wherein said gear retainer means comprises a gear retainer and aretainer cover.
 3. The seat belt retractor according to claim 1 whereinsaid gear means includes a drive gear rotatable with said spool.
 4. Theseat belt retractor according to claim 3 wherein said gear meansincludes a reduction gear meshing with said drive gear and said ringgear.
 5. The seat belt retractor according to claim 1 wherein said modeswitching lever includes an extending arm engageable with said lockingbar.
 6. The seat belt retractor according to claim 1 wherein said modeswitching lever includes at least one arm engageable with said tabmeans.
 7. The seat belt retractor according to claim 1 wherein said tabmeans comprises first and second tabs located on the periphery of saidring gear.
 8. The seat belt retractor according to claim 7 wherein saidmode switching lever includes first and second tab engaging arms,wherein said first ring gear tab engages said first tab engaging arm tourge said mode switching lever to said engaged position and said secondring gear tab engages said second tab engaging arm to urge said modeswitching lever to said disengaged position.
 9. The seat belt retractoraccording to claim 1 wherein said tab means are positioned such thatsaid mode switching lever moves to said engaged position at near fullextension of said belt webbing thereby switching said retractor to saidautomatic locking mode and said mode switching lever moves to saiddisengaged position at near full retraction of said belt webbing therebyswitching said retractor to said emergency locking mode.
 10. The seatbelt retractor according to claim 1 further comprising a rewind springassembly mounted directly onto said gear retainer means and engagingsaid belt support shaft.
 11. The seat belt retractor according to claim10 wherein said gear retainer means is mounted to said frame adjacentone end of said spool and said inertia sensitive actuator is mounted tosaid frame and adjacent the opposite end of said spool.
 12. In a seatbelt retractor of the type having a retractor frame, a spool carried bysaid frame defined by a belt support shaft and having at least onetoothed sprocket, seat belt webbing connected to said spool, a lockingbar carried by said frame and movable between an engaged position withsaid toothed sprocket, thereby inhibiting withdrawal of said webbing, toa disengaged position from said toothed sprocket, thereby permittingwithdrawal of said webbing, said retractor further having an inertiasensitive actuator which acts upon said locking bar in response todeceleration forces above a predetermined level to urge said locking barinto said engaged position, the improvement for enabling said seat beltretractor to be operated either as an emergency locking retractor whichprevents said seat belt webbing from being withdrawn when said retractoris subjected to deceleration above said predetermined level, or as anautomatic locking retractor which permits retraction of said webbing butinhibits withdrawl of said webbing, comprising:gear retainer means, adrive gear carried by said seat belt support shaft for rotationtherewith in position coaxially with said belt support shaft saidtoothed sprocket being fixed to said shaft, a reduction gear meshingwith said drive gear, a ring gear meshing with said reduction gearwhereby said ring gear rotates with rotation of said drive gear and at arate of rotation less than that of said drive gear, tab means on saidring gear, a mode switching lever having a spring arm and beingrotatable about a pivot means from an engaged position directlycontacting said locking bar and resiliently urging said locking bar intoengagement with said toothed sprocket to a disengaged position from saidlocking bar, spring means acting on a fixed point on said mode switchinglever spring arm to exert an extension force between a mounting pivotand said mode switching lever spring arm wherein when said modeswitching lever is in said engaged position said extension force isdirected along one side of a line between said mounting point and saidpivot means thereby biasing said mode switching lever in said engagedposition, and wherein when said mode switching lever is in saiddisengaged position said extension force is directed along an oppositeside of said line thereby biasing said mode switching lever in saiddisengaged position whereby rotation of said ring gear causes said tabmeans to engage said mode switching lever to move said mode switchinglever between said engaged and disengaged positions whereby saidretractor functions as an automatic locking retractor when said modeswitching lever is in said engaged position or an emergency lockingretractor when said mode switching lever is in said disengaged position.13. The seat belt retractor according to claim 12 wherein said gearretainer means comprises a gear retainer and a retainer cover.
 14. Theseat belt retractor according to claim 12 wherein said switching leverincludes an extending arm engageable with said locking bar.
 15. The seatbelt retractor according to claim 12 wherein said switching leverincludes at least one arm engageable with said tab means.
 16. The seatbelt retractor according to claim 12 wherein said tab means comprisesfirst and second tabs located on the periphery of said ring gear. 17.The seat belt retractor according to claim 16 wherein said switchinglever includes first and second tab engaging arms, wherein said firstring gear tab engages said first tab engaging arm to urge said switchinglever to said engaged position and said second ring gear tab engagessaid second tab engaging arm to urge said switching lever to saiddisengaged position.